1. Field of the Invention
The present invention relates to the field of data communication in satellite communication systems. The present invention specifically relates to a method of communicating signal data in a global navigation satellite system (GNSS) using low density parity check (LDPC) convolution codes and a system thereof under low signal to noise ratio condition.
2. Description of the Prior Art
Communication systems transmit information from one source to another across various communication channels. In particular, satellite communication systems are implemented to provide a basic communication, i.e. space-to-earth communication and space-to-space communication through the communication channels. Initially, the information to be transmitted is encoded at source end. After source coding, channel coding techniques are implemented to the information before transmitting it to the communication channels. The channel coding techniques are used to protect the data from channel noise. These coding techniques are commonly referred as Forward Error Correction (FEC) coding techniques such as Bose-Chaudhuri-Hocquenghem (BCH) codes, Convolutional codes, Turbo Codes and LDPC block codes.
Further, the channel coding techniques are judged based on their ability to approach Shannon's capacity limit, which states that as long as the transmission rate is less than the channel capacity, error free communication can be achieved. Generally, BCH codes, Convolutional codes and Turbo Codes are used for channel coding in many applications. Then, Low Density Parity Check (LDPC) block codes are introduced for achieving higher capacity performance over a variety of channels than other channel coding techniques.
LDPC convolution codes (LDPCCC) are introduced as convolution counterparts of LDPC block codes. LDPCCC is capable of achieving similar capacity approaching performance as LDPC block codes with simple encoding and decoding. In addition, LDPCCC is suitable for continuous as well as block transmission. Moreover, it uses iterative decoding offering excellent Bit Error Rate (BER) performance and is amenable to pipelining VLSI implementation of LDPCCC encoders and decoders is accomplished based on replicating units such as processors. For the same complexity of hardware, LDPCCC outperforms other FEC techniques such as BCH, Convolutional codes, Turbo Codes and LDPC block codes.
Such LDPCCC technique provides very good BER performance with simpler hardware implementation for error free performance over a variety of communication channels. However, so far, there is no application and implementation of the LDPCCC technique for communication of navigation data structures in a conventional medium earth orbit or geostationary orbit satellite navigation system. Further, it is necessary to maintain error free performance over the communication channels even in the communication of navigation data structure while implementing the LDPCCC technique in Global Navigation Satellite System (GNSS). Therefore, it is desirable to provide a method and system of communicating signal data in GNSS system using LDPC convolution codes, which is capable of achieving near error free performance over a GNSS communication channel for effective navigation data communication.